1. Field of the Invention
The present invention relates to a controlling device for controlling a range switch mechanism to change (switch) a shift range of the range switch mechanism by driving and controlling a motor in accordance with a range switch operation by an occupant.
2. Description of Related Art
Recently, as JP-A-2002-286128 and JP-A-2004-23932 disclose, a vehicle has become electronically controlled, and a system has been developed for detecting with a switch a range switch operation (shift lever manipulation) by an occupant, and for driving and controlling a motor based on the detection signal to change the shift range of a range switch mechanism into a required shift range required by the occupant.
As shown in FIG. 5, every time the range switch operation is performed to change the shift range into the required shift range, the motor is started accordingly and is stopped after the shift range of the range switch mechanism has been changed into the required shift range, and the start and stop are is repeated. While the motor is energized, a coil of the motor and a drive circuit generate heat. Therefore, while the motor is stopped, the heat generated by the energization of the motor is released such that a temperature of the motor is lowered (e.g., a motor stop period, where the motor is stopped, serves as a motor cooling period).
In general, while the vehicle travels, the occupant may not frequently change the shift range from a traveling range (e.g., D range) into another. However, when the vehicle is stopped, the occupant may frequently perform a needless range switch operation for a pastime (e.g., for pleasure), because the shift range is changeable into any shift range while the vehicle is stopped. In a case, where the range switch operation is frequently repeated, the motor stop period (motor cooling period) may be shortened or become zero for each of the range switch operation. As a result, an increase of the temperature due to the heat generation by the coil of the motor and the drive circuit may not be limited, and thereby the coil of the motor and the drive circuit may have excessively high temperature. Thus, this may decrease duration of life of the system and may cause a malfunction of the system.